1. Field of the Invention
This invention relates to a composite racket, and particularly to a composite racket which is made of a thermoplastic resin with a continuous fibrous matrix in at least one portion thereof and made of a thermosetting resin with a continuous fibrous matrix at the other portion.
2. Brief Description of the Prior art
It has been known that racket frames made of epoxy resins provide the advantages of high rigidity, good striking characteristics and easy fabrication. However, such racket frames produce substantial initial shock which will cause injury to the users and, in addition, cannot provide a sufficient impact strength Attempts were made to improve the impact strength and reduce initial shock or vibrational forces by altering the fibrous materials used in combination with the epoxy resins or by modifying the orientations of fibers. Nevertheless, the improved effects obtained thereby are not satisfactory owing to the limitation of using a single type of matrix resin. Use of a thermoplastic resin such as Nylon in the fabrication of the racket frame has been recently suggested for the purposes of reducing initial shock and vibrational forces and improving the impact strength. However, the high flexibility of the thermoplastic resin lowers the striking characteristics and the fabrication of a racket with a composite thermoplastic material is difficult.
U.S. Pat. No. 5,071,125 which is owned by the applicant of this invention discloses a racket which is made of two or more than two materials. It also discloses a preferred embodiment comprised of a head made of a material of high rigidity and a shaft made of a less rigid or stiff material so as to reduce shock transmitted to the hand of the user.
There are other patents such as U.S. Pat. Nos. 4,367,871, 4,052,060, 4,725,059, 4,746,119, 4,906,002 and 4,007,929 which concern the connection of two or more than two component parts of a racket frame. A composite racket disclosed in U.S. Pat. No. 4,725,059 comprises a shaft portion, two branches of a throat portion and a frame portion all of which are made of composite materials Each portion has a foam core and a sheath comprised of fiber webs or braids impregnated with a synthetic resin. The foam cores and the sheaths of the portions are made of different materials.